Double Etch\nMethod for the Fabrication of Nanophotonic\nDevices from van der Waals Materials

The\nintegration of van der Waals (vdW) materials into photonic\ndevices has laid out a foundation for many new quantum and optoelectronic\napplications. Despite tremendous progress in the nanofabrication of\nphotonic building blocks from vdW crystals, there are still limitations,\nspecifically with large-area devices and masking. Here, we focus on\nhexagonal boron nitride (hBN) as a vdW material and present a double\netch method that overcomes problems associated with methods that employ\nmetallic films and resist-based films for masking. Efficacy of the\ndeveloped protocol is demonstrated by designing and fabricating a\nset of functional photonic componentsincluding waveguides,\nring resonators, and photonic crystal cavities. The functionality\nof the fabricated structures is demonstrated through optical characterization\nover several key spectral ranges. These include the near-infrared\nand blue ranges, where the hBN boron vacancy (V<sub>B</sub><sup>–</sup>) spin defects and the coherent B center quantum emitters emit, respectively.\nThe double etch method enables fabrication of high-quality factor\noptical cavities and constitutes a promising pathway toward on-chip\nintegration of vdW materials.